The Gordon Conference on "Cellular and Molecular Bioenergetics" will be held June 20-25, 2004 at Proctor Academy in Andover, New Hampshire. The traditional focus of this meeting has been on the mechanisms of oxidative phosphorylation and electron transport. Although these continue to be central themes the forthcoming conference will also focus more on cellular and molecular aspects of bioenergetics. This meeting has traditionally been a forum for presentation of high resolution structures of membrane proteins and many of these structures have been first presented at this venue. In addition, to the presentation of X- ray structures the meeting also presents mechanistic information about membrane proteins using spectroscopic, biophysical, molecular, and cellular techniques. Recently discussed systems at this meeting include the lac permease, ABC transporters, respiratory complexes II, III and IV and ATP synthase. In addition the meeting has expanded into cellular bioenergetics and disease, with presentations on V-ATPases, and the mechanisms and targeting of bioenergetic complexes. In the 2004 meeting presentations will be made on recent high resolution structures of membrane proteins and methods used to analyze electron and proton transport mechanisms and ways the protein environment controls the redox potentials of cofactors used for electron transport. An expanding area of interest is the role mitochondria play in the aging process and how assembly and function of the respiratory chain contributes to aging and disease. Several sessions in the 2004 conference will be devoted to this theme to bring together structural, mechanistic, and cellular/molecular approaches to understanding cellular bioenergetics. The participants in the Molecular and Cellular Bioenergetics conference include the leaders in the field, drawn from academics, government, industry, including junior scientists, such as graduate students/postdoctoral fellows. The Gordon conference is organized to maximize opportunity for discussion and presentation of the latest findings in this area.